The invention relates to fabric for paper making machines and, more particularly, to a seam press fabric.
Paper is conventionally manufactured by conveying a paper furnish, usually consisting of an initial slurry of cellulosic fibers, on a forming fabric or between two forming fabrics in a forming section, the nascent sheet then being passed through a pressing section and ultimately through a drying section of a papermaking machine. In the case of standard tissue paper machines, the paper web is transferred from the press fabric to a Yankee dryer cylinder then creped.
Paper machine fabric or clothing is essentially employed to carry the paper web through these various stages of the papermaking machine. In the forming section, the fibrous furnish is wet-laid onto a moving forming wire and water is encouraged to drain from it by means of suction boxes and foils. The paper web is then transferred to a press fabric that conveys it through the pressing section, where it usually passes through a series of pressure nips formed by rotating cylindrical press rolls. Water is squeezed from the paper web and into the press fabric as the web and fabric pass through the nip together. Press fabrics generally comprise a batt of fibers needled to a base fabric. In the final stage, the paper web is transferred either to a Yankee dryer, in the case of tissue paper manufacture, or to a set of dryer cylinders upon which, aided by the clamping action of the dryer fabric, the majority of the remaining water is evaporated.
The base fabrics of press felts are woven endless, whether they are seamed or not, such that the yarns of the weft in the loom lie in the machine direction of the fabric on the paper machine. The weft yarns weave back and forth continuously between the laterally extending edges of the fabric and form a seam loop at the reversals on one side. The two ends formed are then joined together on the machine by means of a pintle wire.
Press felts consist of multiple layers which are secured together by needling. This works by mechanically locking the constituent batt fibers into various layers and in so doing holds them together. In addition, the batt fiber gives a homogenous paper support surface.
Thus, in the paper making industry, paper making felts or fabrics are used to carry the cellulosic material as it is formed into paper, and one such fabric is an endless woven base with a pin seam for securing the ends of the fabric together once the fabric is in place on the machine.
Numerous disclosures have been made in connection with manufacture of pin seam fabrics, including U.S. Pat. Nos. 6,283,165, 6,000,441, 3,283,388 and 4,495,680 as non-exhaustive examples. These teachings and others tend to be costly and slow, and the need remains in the industry for reduced cost and faster delivery time.
It is the primary object of the invention to provide a press fabric which meets these needs.
Other objects and advantages will appear below.